From: Mel Gorman <mel@csn.ul.ie>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/7] mm: vmscan: Convert lumpy_mode into a bitmask
Date: Wed, 1 Dec 2010 10:50:29 +0000 [thread overview]
Message-ID: <20101201105029.GL13268@csn.ul.ie> (raw)
In-Reply-To: <20101201102732.GK15564@cmpxchg.org>
On Wed, Dec 01, 2010 at 11:27:32AM +0100, Johannes Weiner wrote:
> On Mon, Nov 22, 2010 at 03:43:50PM +0000, Mel Gorman wrote:
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -51,11 +51,20 @@
> > #define CREATE_TRACE_POINTS
> > #include <trace/events/vmscan.h>
> >
> > -enum lumpy_mode {
> > - LUMPY_MODE_NONE,
> > - LUMPY_MODE_ASYNC,
> > - LUMPY_MODE_SYNC,
> > -};
> > +/*
> > + * lumpy_mode determines how the inactive list is shrunk
> > + * LUMPY_MODE_SINGLE: Reclaim only order-0 pages
> > + * LUMPY_MODE_ASYNC: Do not block
> > + * LUMPY_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
> > + * LUMPY_MODE_CONTIGRECLAIM: For high-order allocations, take a reference
> > + * page from the LRU and reclaim all pages within a
> > + * naturally aligned range
>
> I find those names terribly undescriptive. It also strikes me as an
> odd set of flags. Can't this be represented with less?
>
> LUMPY_MODE_ENABLED
> LUMPY_MODE_SYNC
>
> or, after the rename,
>
> RECLAIM_MODE_HIGHER = 1
> RECLAIM_MODE_SYNC = 2
> RECLAIM_MODE_LUMPY = 4
>
My problem with that is you have to infer what the behaviour is from what the
flags "are not" as opposed to what they are. For example, !LUMPY_MODE_SYNC
implies LUMPY_MODE_ASYNC instead of specifying LUMPY_MODE_ASYNC. It also
looks very odd when trying to distinguish between order-0 standard reclaim,
lumpy reclaim and reclaim/compaction.
> where compaction mode is default if RECLAIM_MODE_HIGHER, and
> RECLAIM_MODE_LUMPY will go away eventually.
>
> Also, if you have a flag name for 'reclaim with extra efforts for
> higher order pages' that is better than RECLAIM_MODE_HIGHER... ;)
>
> > +typedef unsigned __bitwise__ lumpy_mode;
>
> lumpy_mode_t / reclaim_mode_t?
>
It can't hurt!
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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next prev parent reply other threads:[~2010-12-01 10:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-22 15:43 [PATCH 0/7] Use memory compaction instead of lumpy reclaim during high-order allocations V2 Mel Gorman
2010-11-22 15:43 ` [PATCH 1/7] mm: compaction: Add trace events for memory compaction activity Mel Gorman
2010-11-22 15:43 ` [PATCH 2/7] mm: vmscan: Convert lumpy_mode into a bitmask Mel Gorman
2010-12-01 10:27 ` Johannes Weiner
2010-12-01 10:50 ` Mel Gorman [this message]
2010-12-01 11:21 ` Johannes Weiner
2010-12-01 11:56 ` Mel Gorman
2010-12-02 11:04 ` Johannes Weiner
2010-12-02 12:03 ` [PATCH] mm: vmscan: Rename lumpy_mode to reclaim_mode fix Mel Gorman
2010-11-22 15:43 ` [PATCH 3/7] mm: vmscan: Reclaim order-0 and use compaction instead of lumpy reclaim Mel Gorman
2010-12-01 10:27 ` Johannes Weiner
2010-12-01 10:56 ` Mel Gorman
2010-12-01 11:32 ` Johannes Weiner
2010-11-22 15:43 ` [PATCH 4/7] mm: migration: Allow migration to operate asynchronously and avoid synchronous compaction in the faster path Mel Gorman
2010-12-01 10:28 ` Johannes Weiner
2010-11-22 15:43 ` [PATCH 5/7] mm: migration: Cleanup migrate_pages API by matching types for offlining and sync Mel Gorman
2010-12-01 10:28 ` Johannes Weiner
2010-11-22 15:43 ` [PATCH 6/7] mm: compaction: Perform a faster migration scan when migrating asynchronously Mel Gorman
2010-12-01 10:31 ` Johannes Weiner
2010-11-22 15:43 ` [PATCH 7/7] mm: vmscan: Rename lumpy_mode to reclaim_mode Mel Gorman
2010-12-01 10:34 ` Johannes Weiner
2010-11-22 16:01 ` [PATCH 0/7] Use memory compaction instead of lumpy reclaim during high-order allocations V2 Andrea Arcangeli
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